Classification and staging of retinoblastoma

Classifying and staging retinoblastoma is an essential first step when planning how to manage a child with the condition; it also gives important information about prognosis. 
 
Classification schemes in cancer are mainly used to compare the results of different treatments and to enable a prognosis to be given.

C lassification schemes in cancer are mainly used to compare the results of different treatments and to enable a prognosis to be given.

Classification of extraocular disease
If retinoblastoma is left untreated, it will extend beyond the eye. Unfortunately, this is the type most commonly seen in low-and middle-income countries. The tumour can penetrate the globe wall and be visible in and around the eye. It can also reach the central nervous system via the optic nerve, or it can spread to other parts of the body via the blood stream (metastases).
In 2006, Chantada and colleagues developed the International Retinoblastoma Staging System (IRSS; Table 1). 1 It sub-classifies the disease from stage 0-IV. Stage 0 is intraocular disease, usually having a good outcome with treatment, and stage IV is retinoblastoma with metastases, which has a poor prognosis.

Classification of intraocular disease
For intraocular retinoblastoma, the first classification system was introduced by Reese and Ellsworth (R-E) in the 1960s to predict the chances of saving the eye following external beam radiotherapy. When intravenous chemotherapy for intraocular retinoblastoma was introduced in the 1990s, the R-E classification system was no longer appropriate and a new classification scheme, the International Intraocular Retinoblastoma Classification (IIRC) scheme, was developed. 2 The IIRC scheme groups tumours from A-E, depending on their size, location, and additional features,

Classification and staging of retinoblastoma
Classifying and staging retinoblastoma is an essential first step when planning how to manage a child with the condition; it also gives important information about prognosis. • For eyes in group D: the globe could be salvaged in 47% of eyes.
• Group E eyes underwent primary enucleation and were excluded from analysis.
Both the IIRC and ICRB classification systems (see Table 2, overleaf) are now used as the main classification schemes for intraocular retinoblastoma and serve clinicians and researchers across the world. 4 The images in Figure 1 correspond to each category.
Intravenous chemotherapy was found to be effective in treating tumours confined to the retina; however, vitreous seeds seemed to be resistant to the treatment. In 2012, The cTNMH scheme is available in the online edition of this article. www.cehjournal.org E Large tumour touching the crystalline lens, resulting in elevated intraocular pressure and expanded globe  Munier and colleagues developed a technique for injecting chemotherapy directly into the vitreous cavity. 5 They used a classification system that grouped retinoblastoma seeds, based on their morphology and size, as dust, spheres and clouds. Since the introduction of the intravitreal technique, the classification of vitreous seeds is now commonly used to predict the number of injections needed to control the various seed types. 6 Another classification system that is used for all cancer types, including retinoblastoma, was created by the American Joint Committee on Cancer (AJCC). The TNM scheme classifies cancer according to involvement of the primary site: tumour (T), lymph nodes (N) and presence of systemic metastasis (M). The recently published 8th edition includes a hereditary (H) component for Rb, making it the cTNMH scheme (c for clinical). The cTNMH categories are based on whether the tumour burden is determined to be intraretinal, intraocular, advanced intraocular or extraocular. 7 The TNM scheme also has a pathological (pTNM) sub-classification which is widely used by ophthalmic pathologists. Read this article online to see the full scheme: www.cehjournal.org.

Summary
Classification and staging systems for retinoblastoma have evolved as new treatments became available. Several schemes are currently available. For disease confined to the globe, the IIRC, ICRB and cTNMH systems are available, along with additional classifications describing vitreous seeds. For extraocular disease, the IRSS and cTNMH schemes can be used.